The invention concerns a starter device for an internal combustion engine having an electric starter motor as well as a power supply and an activating unit for this starter motor.
Common conventional electric starter motors are usually commutator DC motors with permanent-magnet or electrical excitation. Power is supplied via the electrical system of the vehicle outfitted with the internal combustion engine, by way of its battery.
A more or less complex switch device is generally used as the activating unit for the starter motor, which switch device is coupled to the vehicle""s ignition switch and is actuated when the ignition key reaches the xe2x80x9cignition onxe2x80x9d position.
Customary starter devices according to the related art now comprise a design characteristic that is tailored to the starter output at the xe2x80x9cstarting limit temperaturexe2x80x9d. Since they are operated for only a short period of time, they are not designed for long-term output. Thermal overload protection is therefore unnecessary. Due to this design characteristic, known mass-produced starters are optimized in terms of cost and are tailored relatively greatly to the respective application.
It is known that starter devices are faced with conflicting requirements due to their operating conditions. One example is the xe2x80x9ccold-start problemxe2x80x9d. The starter motor itself is required to make high mechanical output available at very low ambient temperatures, because the internal combustion engine is very difficult to turn over due to the high-viscosity lubricant and, therefore, running properties characterized by high frictional forces. This demands high starter output, which must be achieved by drawing the appropriate amount of energy from the power supply via the vehicle""s battery. Especially at low ambient temperatures, on the other hand, the electrical energy available from the vehicle""s battery is greatly restricted, so excessive power output demands must not be placed, in order to prevent breakdown of the battery.
Based on the problem described as an example, the invention is now based on the object of providing a starter device for an internal combustion engine that is capable of being operated in flexible fashion depending on different operating conditions in order to improve the starting conditions, in particular the starter output and starting comfort, combined with an increased service life of the starting system. It should thereby be possible, in particular, to use common starter motors in the form of least-cost, mass-produced assemblies, as before.
According to the defining part of claim 1, this object is attained by means of a characteristic design of the activating unit. Accordingly, the latter comprises circuit-breaker electronics, a control unit, the control output of which is connected to the control input of the circuit-breaker electronics, as well as sensors connected to the inputs of the control unit to register physical parameters relevant to the starting power of the starter motor. Based on the parameters registered by the sensors, the control unit thereby optimizes the start characteristic line for activating the starter motor within the limit values of the physical parameters permissible for this [starter motor]. Starter output is maximized in particular.
In summary, therefore, the start characteristic line can be controlled in such a fashion that no limit valuesxe2x80x94such as mechanical limit values in the form of the maximum speed at which the starter motor turns, thermal limit values in the form of permitted maximum temperatures of the starter motor, magnetic limit values, as characterized by the current flowing through the starter motor during the starting process, as well as electrical limit values defined by the xe2x80x9cbrush arcingxe2x80x9d and the commutationxe2x80x94are exceeded.
In a preferred exemplary embodiment of the invention, the characteristic line values can then be adapted within the permissible limit values of the physical parameters to optimal parameters identified and specified for the respective starter type and certain starting scenarios.
According to further preferred embodiments of the object of the invention, temperature sensors are provided to register the temperature of the internal combustion engine and/or the starter motor as physical parameters. Moreover, in addition or as an alternative, an ammeter can be provided to register the current flowing through the starter motor during the starting process, a torque sensor can be provided to register the torque produced by the starter motor during the starting process, and/or a speed sensor can be provided to register the speed at which the starter motor turns during the starting process. Depending on the starting temperature, therefore, the characteristic line values can be limited with regard for power and adjusted depending on the temperature of the internal combustion engine, for example.
According to further preferred exemplary embodiments, the start characteristic line can be selected differently depending on various speed ranges. In the low-speed range, for example, the start characteristic line can be selected to limit starting current/torque depending on the permissible demagnetization limit of the starter motor magnets. In the middle-speed range, the start characteristic line, on the other hand, can be selected to limit starting current/torque depending on the permissible, brush arcing-induced wear values, the starter temperature, and/or the temperature of the internal combustion engine. In the higher-speed range, the start characteristic line can be selected depending on the permissible, centrifugal force-induced mechanical limit values of the starter motor.
In all optimization processes, the engine-starting sequence can preferably be registered by the control unit, and the characteristic line values can be changed, particularly in terms of improving the next starting sequence. If the engine does not start, this means that the characteristic line values are changed in terms of improving the starting process so that a repeat start is initiated using the new characteristic line values.
In summary, the object of the invention with its preferred further developments offers the following advantages compared to starter devices based on the related art:
Power can be increased by a factor of 2 at the least.
The increase in warm-start power in the middle speed range in particular leads to improved support as the engine runs up to speed, as well as to shorter start times and an improved starting behavior of the internal combustion engine.
The start characteristic lines can be adapted to identified parameters that are optimal for starting.
At cold-start temperatures, the starting energy can be reduced to protect the battery.
Starting current spikes and, as a result, starting power spikes are prevented.
The starter device offers an integrated, thermal, mechanical and magnetic overload protection. The number of different starter types for different vehicles and internal combustion engines can thereby be reducedxe2x80x94using a fixed hardware configurationxe2x80x94by adapting the control unit parameters to the respective vehicle data.
In general, the size of the starter devices can be reduced while retaining at least the same starter output as compared to conventional systems.